The invention relates to a digital solid-state trip unit for an electrical circuit breaker. The development of microprocessors has enabled digital techniques, whose reliability and scope for adjustment and adaptation to a large number of functions are well known, to be implemented in electrical circuit breaker trip units. The wide range of fault currents processed by the trip unit, the ratio of which may be 30 to 1, and the tripping accuracy required, involve representative numbers of a high value, for example coded in 12 bits. 12-bit components, notably 12-bit analog-to-digital converters, are costly and slow, and this handicap limits the possibilities of using this technique.
The object of the present invention is to enable a wide range digital solid-state trip unit to be produced using low resolution components.